1. Field of the Invention
The present invention relates to an image signal processing (ISP) method and apparatus for processing images, and more particularly, to a technique for processing image signals sensed by an image sensor.
2. Description of the Related Art
In order to properly display a color image, three colors, that is, red (R), green (G), and blue (B) samples, should be necessary to each pixel. However, installing a plurality of color filters for filtering three colors from each pixel makes the structure of an image signal processing (ISP) apparatus complicated and is not preferred in view of costs.
For this reason, a digital image input apparatus, such as a digital camera and a cellular phone in which a camera is installed, uses a color filter array (CFA) such as a bayer filter for filtering only one color from each pixel to reduce the number of color samples. And, the bayer pattern, which is output by an image sensor, is processed by an image signal processor (ISP) to create an RGB full color image.
The image signal processor performs two important functions: one of which is an image denoising (or noise reduction) function for effectively eliminating or reducing noise existing in an image, and the other of which is an interpolation (or demosaicing) function for obtaining an RGB full color from color patterns output by an image sensor.
Generally, a method which performs interpolation and then performs image denoising, as illustrated in FIG. 1, or a method which performs image denoising and then performs interpolation, as illustrated in FIG. 2, is being widely utilized.